A tubular rotating scrubber for removing sulfur dioxide from stack gases by tumbling contact of a lime slurry was invented by Clifford J. Lewis and constitutes the subject of U.S. Pat. No. 4,060,587. Such apparatus and its method of operation are also described in the following publications and various oral presentations of similar context:
(1) Lewis, C. J., "New Concept for Scrubbing Gases," Brick and Clay Record, June, 1973;
(2) Lewis, C. J., "Lime, Limestone Employed in New Gas Scrubbing Concept," Pit and Quarry, July, 1973;
(3) Lewis, C. J., "Aqueous Lime Scrubber Simplifies Sulfur Dioxide Removal," Rock Products, July, 1974.
The Lewis system effectively removes sulfur dioxide from a flue gas, but the waste sludge product normally contains from about 50 to 80 percent by weight of free moisture. This sludge poses a waste solids disposal problem because of its semisolid nature and substantial quantity. An object of this invention is to provide a scrubber for removing sulfur dioxide from flue gas which minimizes the amount of free moisture in the waste product. A further object is to provide a process for such sulfur dioxide removal which also furnishes a slurry product which is suitable for use as landfill.